Born in Virginia in 1815, Johnston was orphaned before his 10th birthday. As a result, he entered into an apprenticeship as a tailor. Over the years he lived in Philadelphia, New York City, Savannah and Augusta. At the age of 21 he entered the Seminole War, and moved to Columbus, Mississippi, immediately afterward. He lived in Mississippi for the remainder of his life, dying in 1916.

During the Civil War, Johnston sided with the Union. For his loyalty, the federal government made him the agent who was responsible for collecting confiscated cotton.

He became wealthy and socially prominent as a result of his successes with real estate and textile manufacturing.